Nice looking aluminium parts, it will be interesting to see how much improvement there has been, and maybe you could say which new parts made improvements and which parts did not.
Last edited by EddyCurrent; 26-11-2014 at 10:46 AM.Spelling mistakes are not intentional, I only seem to see them some time after I've posted
26-11-2014 #24Spelling mistakes are not intentional, I only seem to see them some time after I've posted
Eddy, I've made all the changes together so won't be able to measure individual contributions but my best guess at where any improvements would come from are:
1. Y axis ballscrew plate changed from 18mm plywood to 20mm aluminium (forms part of the 'box' assembly at the top of the Y axis)
> Should improve Y direction stiffness
2. Z axis thin wall aluminium box section and plate arrangement with large offset from gantry changed to 20mm aluminium plate with pockets and lower gantry offset
> Should improve X direction stiffness, plus some Z and some Y due to having much less offset from the gantry
3. Spindle mounting bracket changed from a pair of 20mm thick clamping plates to a converted linear bearing housing
> Probably wasn't a limiting factor in the previous machine, but would in theory improve all 3 directions a bit.
Obviously don't try this at home but whilst I cut out my first part last weekend (from 10mm aluminium) I touched various parts of the machine and felt the vibrations. Not the most scientific method, but found the following, working back from the tool:
Spindle vibration high (not excessive or troubling but high relative to the other points)
Z axis plate vibration high
Z axis rail vibration fairly high
Z axis carraiges (which are on the Y axis) medium /medium low
Y axis assembly medium / low
Gantry sides low
In other words the biggest delta was across the Z axis linear profile bearings, in particular the top one which is the one further from the tool. These are 15mm units. If I was to start again I'd go with 20mm units as they are stiffer, plus they are a bit easier to mount (15mm rails take M3 bolts!), involve less pocketing, plus other general advantages.
But I'm pleased with the progress and if everything is as good as it can be and I've hit the limit of the rail then its not such a bad place to be.
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This seems quite an upgrade to me. Plus more pleasing to the eye, call me crazy but that's quite important to me.
Before you ask - no I still haven't measured the stiffness of the new machine! But I have managed to make progress on the semi-automatic dust shoe system, and as you can see it is making nice cuts in aluminium.
The bits assembled on the bench. Used 12mm stainless rod and linear bearings for the rise and fall bits.
I posted ages ago about the concept in another post, but made more sense to tack it on the end of this. To re-cap,
The dust shoe has a removable lower section, held on by magnets plus located by the ends of the support rods. This is to allow easy bit changes. It also allows a variety of dust shoes to be fitted depending upon the job.
Semi-automatic height adjustment
It is attached to the Y axis, not the Z axis, so it does not simply rise and fall with the cutter. Instead there are 2 adjustable knobs, one to control the maximum raised position, and one to control the maximum lowered position.
Initially at the home (or raised Z position) the dust shoe is held up by the lower adjustment tab, which rides on top of the spindle body. When the cutter drops down the dust shoe drops with it.
As the cutter approaches the cutting position the upper knob and stop-collar prevent the dust shoe falling any further, being set to be just above the top of the workpiece (say 2mm). During cutting, even deep plunging, the dust shoe is always at 2mm above the workpiece irrespective of cutting depth as the spindle moves independantly of the dust shoe. This should make it good at collecting dust, and avoid the problem of crushed brushes or brushes being sucked into the extractor or cut with the cutter etc.
When the cut is finished the Z axis raises up and at some point collects the dust shoe tab which raises the dust shoe as well. It is then ready for a bit change, or the next cut.
Here are the parts fitted to the machine:
Here is a close up showing the 2 adjustors for the max and min height adjustors.
Still have to cut a short length of 100mm duct to fit between the lower part and the fixed part, plus add the 100mm duct from the extractor machine, but you should get the idea. All sounds OK in theory so will let you know if it actually works!
Very nice idea with the dust shoe. if you use some advanced CAM you could control all tool paths so no problem will arise. It seems even with simpler CAM it should work ok.
By the way i have a very similar dust shoe setup, only thing is that it does not slide like yours. Biggest problem i have encountered is when something chips and stucks in the section between the spindle and the vacuum hose. But my dust shoe seems not so deep like yours. So your should work better. i believe this dust shoe design will work better with short brush
Nice looking dust shoe, I need to study it better when I get time. I liked this idea, don't know if it can be applied to your; https://www.youtube.com/watch?v=tBzoQw4du8ESpelling mistakes are not intentional, I only seem to see them some time after I've posted
I guess you mean CAM toolpath control to avoid any clamps? I have some low profile clamps so should be OK there.
With regard to adding brushes - yes I've considered that and with the lower plate being removable I can try different designs and use the best one for the job.
Thanks for the link to the video. He does go on a bit! During cutting mine will behave a bit like that, but with the advantage of rising up out of the way when the cut is finished. His looked static from what I could tell.
Also, the lower plate on his is completely open, whereas mine is only open locally around the cutting bit so should give better extraction. I also think my magnetic removable plate means it is quick to get everything out of the way and change over to jobs which don't really need a dust shoe such as aluminium machining.